1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.jxpath.functions;
19
20 import java.lang.reflect.Constructor;
21 import java.lang.reflect.InvocationTargetException;
22
23 import org.apache.commons.jxpath.ExpressionContext;
24 import org.apache.commons.jxpath.Function;
25 import org.apache.commons.jxpath.JXPathInvalidAccessException;
26 import org.apache.commons.jxpath.util.TypeUtils;
27
28 /**
29 * An extension function that creates an instance using a constructor.
30 */
31 public class ConstructorFunction implements Function {
32
33 private static final Object[] EMPTY_ARRAY = {};
34 private final Constructor constructor;
35
36 /**
37 * Constructs a new ConstructorFunction.
38 *
39 * @param constructor the constructor to call.
40 */
41 public ConstructorFunction(final Constructor constructor) {
42 this.constructor = constructor;
43 }
44
45 /**
46 * Converts parameters to suitable types and invokes the constructor.
47 *
48 * @param context evaluation context
49 * @param parameters constructor args
50 * @return new instance
51 */
52 @Override
53 public Object invoke(final ExpressionContext context, Object[] parameters) {
54 try {
55 Object[] args;
56 if (parameters == null) {
57 parameters = EMPTY_ARRAY;
58 }
59 int pi = 0;
60 final Class[] types = constructor.getParameterTypes();
61 if (types.length > 0 && ExpressionContext.class.isAssignableFrom(types[0])) {
62 pi = 1;
63 }
64 args = new Object[parameters.length + pi];
65 if (pi == 1) {
66 args[0] = context;
67 }
68 for (int i = 0; i < parameters.length; i++) {
69 args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
70 }
71 return constructor.newInstance(args);
72 } catch (Throwable ex) {
73 if (ex instanceof InvocationTargetException) {
74 ex = ((InvocationTargetException) ex).getTargetException();
75 }
76 throw new JXPathInvalidAccessException("Cannot invoke constructor " + constructor, ex);
77 }
78 }
79 }